This simple scenario was used to prepare a sample blend chain. The problem arises on last blend operation (for edge res_27). If the radius of the last blend (0.2) is increased (e.g. to 0.3), then the blend cannot be constructed at all.

Alexey, I have reproduced the issue and noticed that the previously attached screenshot was not relevant. Please, have a look at newly attached pictures. They correspond to the reported scenario and illustrate the problem.